There are various different types of speakers, which may be divided into electronic speakers (i.e. moving coil speakers), electrostatic speakers (i.e. capacitive speakers), electromagnetic speakers (i.e. reed type speakers) and piezoelectric speakers (i.e. transistor type speaker) according to the transduction principle, and the last two types of speakers described above are generally used in rural cable broadcasting networks. Speakers may also be divided into low-frequency speakers, mid-frequency speakers, and high-frequency speakers according to the frequency range, and these speakers are often used as a combination speaker in a speaker box.
According to the mechanism and structure of the transduction, speakers may be divided into moving coil speakers (electronic type), capacitive speakers (electrostatic type), piezoelectric speakers (transistor or ceramic type), electromagnetic speakers (compression spring type), electro-ionic speakers, and pneumatic speakers. The electric speakers with the advantages of good electroacoustic performance, firm structure and low cost have a wide range of application.
According to the sound radiation material, speakers may be divided into paper cones, horns, and diaphragms. According to the shape of paper cone, speakers may be divided into circular, elliptical, double paper-cone and rubber corrugated rim speakers. According to the operating frequency, speakers may be divided into low-frequency, mid-frequency, and high-frequency speakers, and some are divided into speakers specified for the use for answering machines, televisions, regular and high-fidelity. According to the voice coil impedance, speakers may be divided into low-impedance and high-impedance speakers. According to the sound effect, speakers may be divided into straight and surround sound speakers.
Speakers may also be divided into built-in speakers and external speakers, wherein the external speaker generally refers to a speaker box, and the built-in speaker generally refers to a speaker built into a MP4 player, so that users not just can listen to the sound played from the MP4 player through a headset only, but also through a built-in speaker. Therefore, a MP4 player having a built-in speaker no longer needs an external speaker box, and avoid the inconvenience caused by wearing the headset for a long time.
Since a conventional spherical speaker has a poor self-adjusting capability, the spherical speaker cannot confirm its playing mode according to the front car distance of the nearest car ahead in order to provide a reminding effect about a car in the front with different front car distances.
In view of the aforementioned drawbacks of the prior art, the inventor of the present invention based on years of experience in the related industry to conduct extensive research and experiment, and finally provided a feasible solution to overcome the drawbacks of the prior art.